Cubital Tunnel Syndrome (Elbow Ulnar Nerve Entrapment)

What is cubital tunnel syndrome?

Cubital tunnel syndrome is a condition where one of the main nerves of the arm, the ulnar nerve, becomes compressed or irritated at the point of the elbow. The ulnar nerve is a long nerve that can be damaged or diseased in any number of ways, broadly referred to as ulnar neuropathy, but cubital tunnel syndrome is a problem of the ulnar nerve at a specific site – at the elbow. It is often confused with a similar condition of the arm known as carpal tunnel syndrome which affects the median nerve as the wrist joint. In carpal tunnel syndrome, there is numbness and tingling of the little finger and a portion of the ring finger along with slight weakness of the grip.

Ulnar Nerve Entrapment

Location

The ulnar nerve originates from the medial cord of the brachial plexus (C8 to T1) and runs down all the way down to the fingers. At the elbow, the ulnar nerve runs under the medical epicondyle of the humerus, the upper arm long bone. Here a collection of ligaments and fascia forms the tunnel known as the cubital tunnel around the medial epicondyle, the inner bony bump of the elbow. It is at this point that compression of the ulnar nerve is most likely to arise thereby leading to cubital tunnel syndrome. Compression of the ulnar nerve lower down in the Guyon tunnel by the wrist is a separate condition.

Picture from Wikimedia Commons

Compression and Irritation

The ulnar nerve can become irritated or compressed for various reasons. Irritation is more likely to arise with prolonged stretching of the ulnar nerve. Normally the nerve is able to stretch for short periods of times when the elbow is bent. Compression of the nerve tends to occur when the tissue around it presses on the nerve, usually with swelling or enlargement of this tissue. This can occur with injury of the surrounding tissue and elbow dislocation. However, the exact cause of cubital tunnel syndrome is not known.

Effects on the Nerve

Since the ulnar nerve is responsible for the sensory function of the little finger and half of the ring finger, all the way to the back of the palm, any disturbance of the ulnar nerve affects sensation in these areas. Furthermore the ulnar nerve and its branches supply different muscles in the forearm and hand (motor function). In cubital tunnel syndrome the motor activity will therefore also be affect evident by the muscle weakness seen as a partial loss of grip strength.

Signs and Symptoms

Tingling and Numbness

The main sensory symptoms are tingling and numbness, which patients often describe as the hand falling asleep. These disturbances in sensation (paresthesia) are usually triggered by or worsened during prolonged bending of the elbow. Action that require repetitive bending and straightening may also trigger episodes of tingling and numbness.

Elbow Pain

Pain is usually felt at the elbow where the nerve is irritated or compressed. It often occurs simultaneously with tingling and numbness of the the fingers. The elbow pain can radiate up or down the arm from this point. The pain may vary in nature to some degree but typically feels like the “funny bone pain” a person experience when striking their elbow against an object.

Muscle Weakness

The grip strength is usually diminished to some degree in cubital tunnel syndrome. There may also be some difficulty in coordinating movement of the little finger in particular. It may not always be obvious to the patient and instead noticed as clumsiness with a tendency to drop objects that are being grasped. A person may not be able to pinch “as hard” as they could.

Severe Symptoms

In very severe and prolonged cases, there may be muscle wasting and a clawing of the little finger. This is rare. Muscle wasting is irreversible.

Causes of Cubital Tunnel Syndrome

Irritation and compression of the ulnar nerve at the elbow tends to occur in the following instances :

the ulnar nerve slips out of place – sublaxation.
prolonged external pressure on the elbow – leaning on elbow.
thickening of the joint lining of the elbow.
bands of fascia become tightened around the ulnar nerve.
bony spurs develop from the arm bones and press the ulnar nerve.
space-occupying lesions pressing on the ulnar nerve – tumors and ganglia.
fracture of the bones that meet at the elbow joint.
stretching of the ulnar nerve from prolonged bending.

Risk Factors

Repetitive bending and stretching of the elbow usually related to occupational hazards.
Falls and direct trauma to the elbow joint.
History of elbow joint dislocation or fractures.
Rheumatoid arthritis.
Students leaning on one elbow while studying for long hours.

Despite these possible causes and risk factors, sometimes cubital tunnel syndrome arises without any clear explanation for the cause of the condition.

Tests and Diagnosis

Cubital tunnel syndrome may be diagnosed by the findings of a physical examination along with a medical history indicating the typical symptoms of localized tingling and numbness along with a weakening of the grip in the affected hand. Clinical examination by a doctor will assess the onset or worsening of symptoms with bending the elbow or tapping (Tinel’s sign) on the ulnar nerve at the elbow.

Imaging studies like an x-ray and MRI (magnetic resonance imaging) scan will visualize any compression or narrowing. An electromyography (EMG) may help to assess muscle strength. A nerve conduction study (NCS) may also be conducted for diagnosis of cubital tunnel syndrome. Both an EMG and NCS are helpful in assessing the severity of the condition and subsequent improvement with treatment.

Cubital Tunnel Syndrome Treatment

The key to treating cubital tunnel syndrome is to reduce the activities that exacerbate the condition. However, this is not often possible with occupational hazards. Initially, immobilizing the arm at night an be done with splinting or padding. This prevents a person from keeping the elbow bent while asleep. Should night padding and splinting not provide some relief along with medication then daytime immobilization may also be considered for as long as 3 weeks.

Medication

The two main types of drugs used in the treatment and management of cubital tunnel syndrome includes :

Non-steroidal anti-inflammatory drugs to reduce inflammation and pain.
Steroid injections to reduce inflammation although it is often avoided as there is risk of nerve damage.

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Medication on its own may not be sufficient without making lifestyle changes and immobilizing the elbow joint for a period of time until inflammation subsides. Should it not be effective, surgery is then considered.

Surgery

Surgical treatment of cubital tunnel syndrome is usually reserved for the severe cases where complications like muscle wasting has arisen and other measures have not proven effective. There are three main surgical procedures that may be considered for the treatment of cubital tunnel syndrome.

Cubital tunnel release is a procedure where the tunnel is widened by cutting the ligament forms the “roof” of the tunnel. This releases pressure on the ulnar nerve.
Ulnar nerve anterior transposition is a procedure where the nerve is moved from its normal position behind the medial epicondyle. By moving the nerve to the front, the nerve is not stretched as much during bending of the elbow.
Medial epicondylectomy is a procedure where a portion of the inner bony bump of the elbow (medial epicondyle) is removed. The ulnar nerve lies behind this bony bump and by removing it, the nerve is less likely to get trapped and excessively stretched.

References :

http://orthoinfo.aaos.org/topic.cfm?topic=a00069

http://emedicine.medscape.com/article/1231663-overview

http://www.assh.org/Public/HandConditions/Pages/CubitalTunnelSyndrome.aspx